Apparatus for enameling rectangular wire



E. J. FLYNN APPARATUS FOR ENAMELING RECTANGULARWIRE Filed July 1'7, 1940 Inventor:

His Attorney.

m. n M F J d r a w d E Jan. 19, 1943.

Patented Jan 19, 1943 APPARATUS FOR ENAMELINGY RECTANGULAR, wma

Edward J. Flynn, Schenectady, N. Y., assignor to General Electric Company,

New York a corporation of Application July 17, 1940, Serial No. 345,993

Claims.

This invention relates to an apparatus for coating wire or other metallic conductors of rectangular or substantially rectangular cross-section with a liquid coating composition such as an enamel, varnish, lacquer or the like. The invention is concerned especially with 'the application of viscous coating compositions to wires of substantially rectangular cross-section; such highly viscous compositions including the product resultingfrom condensing an aldehyde, such as formaldehyde, with a hydrolyzed polymerized vinyl ester, such as the hydrolysis productof polyvinyl acetate.

An object of my invention is to provide an improved apparatus for coating rectangular wire or similar elongated metallic conductors with a uniform coating of enamel or the like whereby the thickness of the coating can be easily and definitely controlled.

Another object of my invention is to provide an improved die that will continuously apply limited amounts of coating material to certain selected longitudinal portions of a rectangular or polygonal wire.

A further object of the invention is to provide an apparatus for coating rectangular wire with liquid coating compositions whereby the wire is provided with a film of insulation of uniform thickness about the entire circumference of the rectangular wire.

Another object is to provide rectangular wires with baked films of originally viscous liquid coating compositions which films will be asthick on the edges of the rectangular wire as on the flatter surfaces. As will appear with greater particularity from the claims, this is accomplished by employing a die having an opening of a particular configuration adapted to supply the major portion of the coating material to certain selected longitudinal portions of the wire.

Further objects of my invention will become apparent from the following description of'my invention when taken in connection with. the

, accompanying drawing in which'Fig. 1 is a view in-cross-section of a coating apparatus embodyingthe invention; Fig. 2 shows one type of die incorporating the invention; Fig. 3 isa top view of a portion of the die shown in Fig. 2; Figs. 4 and 5 are cross-sectional views taken along lines 4-4 and, 55 respectively ofFig. 3; and Fig. 6

useful in the insulation of wires of circular crosssection is that in which the Wire after having been provided with a surface coating of liquid coating material is passed through a suitable die wire and provide the wire with thin uniform layers of coating material.

However, it has been found that when wires of rectangular or substantially rectangular cross-section have been coated by this conventional method of drawing the wire through a bath of liquid coating composition, then through a die having a rectangular opening therein, and thereafter baking the coating to harden it on the wire, the resultant baked coating is comparatively thick on the flat surfaces of the conductor and extremely thin on the edges'or angular portions of the conductor clue to the fact that the liquid coating material originally applied as a uniform layer tends to collect on the flat portion-s at the expense of the edges of the wire. Although in the practice of this conventional method of coating wire, a plu rality of coatings are-applied to the wire and each separately baked thereon before the application of the succeeding coating, the ultimate shows cross-sectional views of theiwire and aprbeeninsulated or coated with enamels or other resinous insulating materials by applying the coating material in a liquid state to the conductor and thereafter baking-the conductor to harden the insulation thereon. A process particularly results obtained with rectangular wire are still those described above wherein the amount of insulation on the fiat portions of the rectangular .out by applying comparatively large portions of enamel to the longitudinal-edges ofthe-rectangular wire while maintaining I, the portions of enamel applied to the flatter surface portions at a minimum and thereafter baking the coated wire before the liquid coating material applied to the edgesof the wire has had time to migrate substantially to the flatter surfaces of the wire due v tothe inherent-surface tension characteristics of the ordinary liquid coating compositions.

One suitable apparatus for carrying out myin vention is that shown in the accompanying draw ing. 'With reference tojljig, 1 thereof, there is shown bysway of illustrations. wire. coating apparatus in which'a wire I, drawn from a payoff reel and undera guide "sheavev 3 immersed in liquid coating material such as awire enamel 4 contained in container or'troughi is provided with a thin surface coating, of enamel. The coated 'wire moves upwardly through the die 6 adapted to remove excess enamel therefrom and to apply definite quantities of enamel to selected portions of the wire in accordance with the invention. The die 6, shown in greater detail-in Figs. 2-5, may suitably be of the self-centering floating type such as described in Patent 2,238,575, issued to Adalbert Alexay on April 15, 1941 and assigned to the same assignee as the instant application. This die is supported ,on suitable supporting means such as fingers I attached to the walls of oven 8 at a point above the coating bath. The oven 8 through which the wire passes immediately after leaving the die is provided with electric heating units 9 supported within the insulating oven walls ID. A port H provides means for supplying air to the oven. It will, of course. be understood that any suitable design of baking oven may be employed and that such oven may be heated with gaseous combustion products or any other suitable means instead of the electric heating units shown. The wire with its heathardened insulating coating ofenamel thereon passes over a driving sheave i2 and is thereafter recirculated through the coating material, additional dies and the oven to receive additional layers of coating material or passes over a pulley I3 to a take-up reel (not shown) The die 6, shown in greater detail-in Fig. 3, is a somewhat modified form of the type of die disclosed and more fully described in the previously-mentioned. copending Alexay patent. This die comprises a unitary structure formed from a single sheet of flexible metal which is stamped to provide the necessary openings and extension members. In its final form my die structure comprises two spaced apart side walls l4 extending upwardly to edges l5 and then inwardly to meet along a line i6. Preferably the top of my die between edges I5 is fiat or substantially so. Y

An aperture I1 is provided at the center of the fiat top of the die and is located equidistant from the opposite marginal edges defining the top. The line at which the two walls of the die meet passes through the center of this aperture I! the shape of which will be more fully described hereinafter.

By forming the die of a resilient material which is unafl ected by the liquid coating composition, as for'example, spring phosphor bronze, the bottom wall joining the side walls of the die can be deformed to assure closely fitting reengagement of the sections forming the top after these sections are temporarily separated for insertion of any suitable form. In the specific construction shown in Fig. 2, the lower part of each of the side walls I4 is bent inwardly andupwardly to form extensions ll spaced from the side walls 14. These extensions are bent inwardly to form a bottom section l9 which is provided with a suitable slot 20 arranged to permit vertical movement of the wire or the like therethrough and through the orifice I! provided in the ,top of the die; 'By means of this slot the die and the wire to be coated may be brought into operative relationship merely by separating the sections forming the divided top portion and bringing the edge of the wire through the opening formed fingers 1 extending through the opening between the top portion and the flanges 2|.

The shape of the die opening or wire passage I1 is of particular importance in accomplishing the purposes of my invention and both the size and shape depend not only on the cross-sectional area of the wire to be received therein but also, for example, upon the required thickness of insulation, the total number of coats ultimately to be supplied to the wire, the viscosity and other characteristics of the enamel or coating material employed, and other influencing variables. Preferably the lower edges of the walls of the orifice I! are rounded as shown, for example, in Figs. 4 and 5 in order to obtain the optimum self-centering effect of the die about the wire, which effect is maintained hydraulically by the limited amount of coating material passing upwardly through the die opening with the wire.

Much of the die structure hereinbefore described resembles that of the Alexay die. However, in accordance with my invention, it is intended that this or similar dies suitable for coating a circular or rectangular wire should be modified. to have a die orifice as a whole of the general shape shown in Fig. 3. As shown in this figure, the die orifice as a whole is such that most of the enamel isapplied to the edges of the rectangular wire passing upwardly therethrough while comparatively little is applied to the plane surfaces of the wire. To accomplish these purposes I have provided a substantially rectangular die orifice II considerably larger than the wire to be coated having projections 22, 23, 24 and 25 extending inwardly to partially fill the die opening. The substantially rectangular projections, besides forming a wire passage and centering the wire in the die orifice, also remove most of the liquid enamel from those portions of the wire coming in contact therewith. Thus most of the enamel ultimately applied to the wire passes through the small openings or spaces 26, 21, 28 and 29 between the projections 22, 23, 24 and 25 and the wire I. In this die structure projections 23 and 25 are split along 'line "5 permitting insertion of the wire I into the die aperture.

Clearances between the wire and the projections along the plane portions of the wire, i2 e. between the wire and the walls defining the wire passage, and the comparative size of the spaces between the projections at the edges of the rectangular wire, 1. e. the enamel-applying openings. are determined empirically and may, for example, be in the approximate proportions shown in Figs. 4 and 5, respectivehr shpwing cross-sectional views of the die opening and wire along lines 44 through projections 22 and 24 and along line 5-5 at one of the die openings shown in Fig. 3. Preferably the clearances between the wire and the ends 01' the projections along line 4-4 and the wire and the corresponding projections 23 and 25 should be no more than is necessary to permit free movement of the wire through the at thecorners of this major-"opening to form walls defining smailer'openi'ng's or spaces 26, 21, 2s and 29 forpassage of the enamel.

,My method of coating rectangular wires is probably best described by tracing the passage of a single wire through the coating apparatus such as that hereinbefore described as representing one means for carrying the invention'into eflect. As the uncoated wire having/for example, a

cross-section such as indicated in Fig. 6 by refer ence numeral la passes through the coating material such'as an enamel 4 in trough 5, it picks up an excessive amount of enamel and carries it upwardly to the die 6. As the coated wire passes through the ,die opening or aperture in die 6, those portions of the enamel clinging to /flat surfaces of the wireare substantially re-- moved therefrom by the projections 22, 23', 24 and 25 extending inwardly from each side of the die orificewhich projections also center the die about the wire. The excess enamel so removed either .elsof returns by gravity flow to the enamel bath 5 or mixes with that clinging to the edges of the rectangular wire and due to the upward travel of the wire is carriedbetween through the openings between the adjacent projections of the die in the form of longitudinal ridges adherent to the edges of the, wire. These portions gradually flow to'- gether after the wire leaves the die aperture because, as previously indicated, the tendency for such liquid coating materials is to collect in comparatively thick layers having rounded surfaces on the flatter portions of the wire leaving the relatively sharp edges substantially free of.

enamel. However as the die is located immediately below the baking oven, the heat hardening enamel, particularly the more viscous enamels, becomes baked to a hardened state before adapted to gular wires with insulating films of baked enamupiform thickness around the entire circumference of the wire whichmethod essentially comprises repeatedly applying coating material.

primarily to the edges of the wire and immediately baking the coated wire before the material has to any substantial degree left the edges due to.

surface tension eflects. I

It may be desirable in certain instances to use a series of dies each having a slightly greater disspirit of my invention as long as the die aperture is-such as to apply the major portions of the liquid coating material to the edges of the wire.

What I claim as new and desire to secure by Letters Patent of the United States isi 1. A- die for use in coating rectangular wires with liquid coating materials provided with walls defining a rectangular wire passage and walls defining a plurality of openings interconnected with the wire passage at the corners thereof and v apply liquid coating material to the edgesof the rectangular wire.

2. A die assembly for use in coating rectangular wires comprising resilient members defining a substantially rectangular die orifice somewhat this migration of the coating from the edges to.

the flatter portions of the who has progressed any considerable degree. Thus the baked coating firmly adhering to the wire as the coated wire leaves the oven has a form approximately that shown at lb in Fig. 6 characterized by ridges of baked enamel extending along the edges of the wire.

In coating any type of wire with organic liquid:

enamels, it is customary to pass the wire through the coating apparatus a plurality of times to obtain the proper insulation thickness or build. 0n repeatedly passing the coated wire indicated larger than the wire to be coated, a plurality of rectangular projections extending into said orifice, the extending edges of said projections forming a rectangular passage of substantialy the same size as the wire to be coated, the said proiections cooperating to term a plurality of openby numeral in through the coating material, dies and oven, the liquid enamel applied to the edges of the wire during these subsequent passes has an even greater tendency to flow away from the edges of the wire and towards the centers of the flatter surfaces. This increased tendency is due primarily to the fact that the edges are now substantially ridged and the flatter surfaces somewhat concave as shown at lb and each of these contours favoring the migration of the liquid materlal in the indicated directions to a substantially greater degree than did the purely rightangle edges and substantially plane surfaces of the uncoated wire la. After two or more additional passes of the wire through the apparatus 'the plurality of coats of enamel tend to have the form shown at lo and ultimately, after one or two more passes, that shown at Id in which the baked enamel is of substantially uniform thickness throughout and the edges of the wire are as heavily insulated as the plane surfaces.

- fining a rectangular orifice, rectangular ings adapted, to apply the major portion of a liquid coating material to the edges ofthe rectangular wire to be coated.

3. A die for applying liquid coating material to a rectangular wire, said die having walls jdeo ections extendingfrom each of said walls into said orifice, the extending end portions of said projectlons forming a substantially rectangular-wire receiving passage, the sides of said projections cooperating to form a plurality of openings adapted to apply the major portion of said coating material to the edgesof the rectangular wire to be coated.

4. A die for use in coating wires polygonal in section with liquid coating materials provided with walls defining a polygonal wire passage and walls defining a plurality of openings intercon- *nected with the wire passage; at the corners Thus, it will be seen that I have provided a a thereof and adapted to apply liquid coating material to the edges of the polygonal wire.

5. A die for applying liquid coatingmaterial wires having side surfaces forminggsharpjcorners, said die. having wall portions sha -g form small clearances with central side portions of such wire and other recessed wall portions joining the first-mentioned portions to form large clearanceswith the corners of such wire.

EWARD J. Hum. 

